Shaped charges come in many sizes and shapes and are used mainly for military weaponry and oil well perforating; to a lesser extent demolition and rescue are also users of this complex technology.
The concept of shaping an explosive charge, in order to focus its energy was known in 1792. (“The History of Shaped Charges” Donald R Kennedy)
In 1884 Max von Foerster conducted experiments in Germany showing that a hollow cavity explosive charge will focus the explosive energy and produce a collimated jet of high speed gasses along the longitudinal axis of the cavity, this jet also could penetrate steel.
In 1888, while conducting research for the U.S Navy, at Newport R.I., Charles Munroe discovered that not only could explosive energy be focused, but lining the hollow cavity in the explosive with metal increased the penetration dramatically, the effect is commonly called the Munroe effect.
These discoveries were further studied in 1910 by Egon Neumann of Germany who conducted similar experiment's, which showed that a cylinder of explosive with a metal lined conical hollow cavity could penetrate through steel plates. The military implications of this phenomenon were not realized until the lead up to world war two.
In the 1930's flash x-ray technology was developed which allowed the in depth study of the Shaped Charge jetting process. With this new and other diagnostics, it was possible to take XRay pictures of the collapse of the liner and the resulting jet. This led to a more scientific and complete understanding of the Munroe principle and emphasized the power of shaped charges.
Modern shaped charges as used in anti-tank weapons produce a long stretching rod like metal jet that penetrates about 5 to 8 charge diameters in steel, deeper in masonry or rock. The average diameter of a 5 CD through hole in steel from these charges is less than 15% of the explosive charge diameter (CD) of the device. The holes made by these jets do not provide sufficient diameter to allow follow on or follow through devices to pass into the perforation and add to the hole depth.
There have been some specialized efforts by Haliburton to produce other than conical type shaped charges for special purposes such as pipe cutting and anchor chain cutting. These types of charges are called linear shaped charges and use the two dimensional collapse to produce a thin sheet like jet with somewhat similar cutting power to the usual conical shaped charge. These linear shaped charges are flexible and can be formed by hand into desired shapes. The British Wall AXE circa 1960 is an example of a formable linear shape charge with a wide angle liner; the device is used against light structures such as wooden doors and thin walls and do not give very deep penetration.
Throughout the history of shaped charges the primary effort of research in this field was directed toward depth of penetration by the jet. Although hole size was considered in the past, little research has been done on significantly increasing jet diameter and cross-sectional shape of the jet to produce a larger hole diameter. In oil field applications a larger hole is most desirable as the flow area of the hole increases rapidly with an increase in hole diameter. With the ability to produce a full caliber hole, a follow on or follow through device can be deployed into the hole to the correct standoff from the bottom of the hole. When detonated at the correct standoff this will increase the hole depth by that of the primary hole producing device, this can be repeated numerous times in the same hole.
In the case of oil well stimulation the ability to place lined shaped charges into the formation outside of a casing, not only increases hole depth but blast affects from the HE fractures the local rock increasing its permeability and flow rate. Many other industries can benefit from this innovation from Military to Mining so the motivation to pursue the concept of producing a full caliber hole with a shaped charge is to provide new means to these industries.